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Intercept audio signal from XM radio to do a "nav cut" from your phone

2682 Views 11 Replies 5 Participants Last post by  AZKlaus
I brought this up in an other thread but realized maybe it should be its own discussion as there could be other implications.

With our radios XM comes in from a separate module that is controlled via class 2 serial data and then receive an audio input via 3 wires, radio left, radio right, and common (i'm assuming these are line level). Why is this interesting? A lot of us like to listen to the music on our phones but we also like to listen to XM. And myself personally I use my phone a lot for navigation. The problem is (and this really comes into play for another setup where we can display and control our phones on our touchscreens via a mimicsX2) that if you are listening to XM and have your phone audio plugged in you'll miss your nav directions.

Phones are very good about not broadcasting "dead signals", in otherwords the headphone jacks only send a signal when your phone is generating audio, a lot of this has to do with bluetooth power management but it comes into play on the hardwired headset as well.

This all leads into using an automatic A/B line level switch. What this would do is allow you to listen to XM radio normally as we would convert the outbound pins from the XM controller into RCA, plug them into the input A (constant) and have the RCA output connected into the wires running into the headunit. You would then have your phone connected with a mini to RCA adapter to the B (sensing) input and then when you play either music, navigation, or whatever you would it would sense the signal and switch to the B input.


Clip 3 wires coming out of XM module- BN/WH (L Audio +) D-GN/WH (R Audio +) and YE/WH (common) (see wiring diagram below)

Connect these to the wires coming out of the module:
Each blue wire gets a plus, the white wires connect to the common.
Connect the two RCAs into the A Input of this:
Connect a stereo RCA to (trs) headphone adapter to your phone and then to the B input of the switch. We'd have to play with the sensitivity to see what works best but the delay should be very low so nav instruction start immediately
Take a second set of the 2 channel speaker adapter and connect the RCA side to the output of the switch and the wires to the wiring going back into the headunit same as the input (blues to +, whites to common)

Theoretically you would now have factory style nav interrupt (maybe a call interrupt too?) that you can use with XM radio.

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I was confused for a moment. The write up is written as if this plan would certainly work but then you throw the ‘theoretical’ in at the very end. It is a very interesting idea. I find with modern automotive electronics that there are always a multitude of small details that make what should be a simple, clear-cut garage modification quickly turn into the near impossible.
2 potential issues I see using the audio switch: Would you lose some of the HD quality of the XM signal? The minimum delay is still 0.5 sec. Wouldn't it come in at the middle of a word or you would miss the entire first word of you nav directions? If so, I could see that getting annoying.
Is there not an aftermarket module or kit market that does this or something very similar? Serious question.
Sounds like it can't fail right? Haha. I'm curious as well what the actually delay would be- I'm going to buy one of the switchers and bench test it with some other audio components and see how it is. The signal is likely initiated a portion of a second before the audio actually starts. Worst case it maybe cuts off the "in" of "in 500 feet turn right"? Not sure until I get hands on.

I called PAC about this and they were dumbfounded so I didn't bother. As far as I know there isn't an aftermarket module that already does this.

I did, however, just find this video which seems like a similar concept but using a jack that shorts the connection once you physically plug it in, based on conductivity rather than signal
This gives me confidence that from an audio intercept side this WILL work, it's just a matter of how the switcher actually performs. Time to buy one and try it out :)
I think your audio injection will work, just not sure about that auto switch portion. Also keep in mind no on screen controls of the phone, and the display will always show your XM station info. Minor but something to throw out there.

BTW- I don't know about yours but while my XM sounds acceptably good, my FM sounds better, more HDish really.
Way ahead of you on being able to see and control the phone :)

My XM is very clear, FM to my ear doesn't sound nearly as good, perhaps a little "louder" but only because it lacks some definition. And realistically if all it is is a low level input then the audio quality will be as clear as possible as long as your source is solid.

Once the audio switch comes in I'll post results.

I don't even know whats going on here anymore....
Haha I'll break it down :)

This will let you have a signal sensing Aux input over your XM channel. When you have your phone plugged into this while you listen to XM if your Navigation starts talking or you get some other notification it will cut the XM (like the factory radio does) and play what is coming out of your phone then automatically switch back to XM. This has many standalone benefit especially for those who do not currently have aux in.

People who would use this:
If your factory nav is broken and you want to use your phone nav anyway because the factory nav is terrible compared to google, waze, etc- but you like to jam out to XM and when you do you miss your phone's nav directions because you can't here it over your STP on Lithium
If you have RSE and want a second aux- that way people in the back seat can watch a DVD and you can still have your phone plugged in and listen to your own jams up front
If you are using a MimicsX2 unit to actually view and control your phone on the screen and want to be able to listen to your XM Radio while you do it but still have your nav that you have on the screen function like a factory radio where it cuts the music when turn by turn directions are given.

And I'm sure there's other reasons :)

I told you I'm going to bring some technical stuff to this forum man :)
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AZ - you have a 2010, and a 2010 radio I'm assuming. The 2010 has a lot more guts in it then the earlier models. I don't think a mimics install will work. If the screen/touch sensor wiring is even the same, I don't think you will find room inside for the interface board. The 13/14 radios have plenty of room though, enough to stash a can of soda inside.
Just a heads up as I have completely disassembled both styles.

RE XM - mine doesn't sound bad, but the FM certainly IS louder, and more defined. I'm wondering if the 13/14 radios use an HD radio tuner inside, and the earlier radios used a standard am/fm tuner. It sounds very similar to the Pioneer setup I had with the Pioneer XM tuner and HD radio tuner. I typically stick to XM however as I can't stand commercials or talk radio ;)
I'm going to try using an extra long ribbon cable to try and push it outside of the unit if needed, I did see your prior post in another thread with that warning :)


Very cool!! Does it have the ability to mute my wife?!?

.......That seems to be the biggest factor in my missing some important info I'll never hear again...LOL
See that already provides turn by turn nav whether you like it or not and interrupts a lot more than XM! :rolleyes:
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